A Study Evaluating Trastuzumab Emtansine Plus Pertuzumab Compared With Chemotherapy Plus Trastuzumab and Pertuzumab for Participants With Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Breast Cancer

Inclusion Criteria:

- Histologically confirmed invasive breast cancer with a primary tumor size of greater
than (>) 2 cm

- HER2-positive breast cancer

- Participants with multifocal tumors (more than one tumor confined to the same quadrant
as the primary tumor) are eligible provided all discrete lesions are sampled and
centrally confirmed as HER2 positive

- Stage at presentation: cT2-cT4, cN0-cN3, cM0, according to American Joint Committee on
Cancer (AJCC) staging system

- Known hormone receptor status of the primary tumor

- Participant agreement to undergo mastectomy or breast-conserving surgery after
neoadjuvant therapy

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

- Baseline Left Ventricular Ejection Fraction (LVEF) >/= 55 percent (%) measured by
echocardiogram (ECHO) or multiple-gated acquisition (MUGA)

- Effective contraception as defined by protocol

Exclusion Criteria:

- Stage IV (metastatic) breast cancer

- Participants who have received prior anti-cancer therapy for breast cancer except
those participants with a history of breast lobular carcinoma in situ (LCIS) that was
surgically managed or ductal carcinoma in situ (DCIS) treated exclusively with
mastectomy. In case of prior history of LCIS/DCIS, >5 years must have passed from
surgery until diagnosis of current breast cancer

- Participants with multicentric (multiple tumors involving more than 1 quadrant) or
bilateral breast cancer

- Participants who have undergone incisional and/or excisional biopsy of primary tumor
and/or axillary lymph nodes

- Axillary lymph node dissection or positive sentinel lymph node prior to start of
neoadjuvant therapy

- History of concurrent or previously non-breast malignancies except for appropriately
treated (1) non-melanoma skin cancer and (2) in situ carcinomas, including cervix,
colon, and skin. A participant with previous invasive non-breast cancer is eligible
provided he/she has been disease-free >/= 5 years

- Treatment with any investigational drug within 28 days prior to randomization

- Current National Cancer Institute Common Terminology Criteria for Adverse Events (NCI
CTCAE) version (v) 4.0

- Any significant concurrent medical or surgical conditions or findings that would
jeopardize the participant's safety or ability to complete the study

- Current pregnancy or breastfeeding